This invention relates to a transfer press and more particularly, to a device for positively providing the advance and return movements of the feed bars in the successive increment feed of a work through various operation stations in the transfer press.
Hithereto, as schematically shown in FIG. 1, the conventional transfer press incrementally feeds a work through various operation stations in the press by repeatedly advancing and returning a pair of feed bars 17, 17' each having a plurality of clampers 17a, 17'a, respectively and the timing diagram with respect to varying crank angles in the rotation of the crank in the transfer drive press is as shown in FIG. 2 in which the movement of the feed bars is interrupted after the bars have advanced a work by the angular distance of 120.degree. from the crank angle of 300.degree. through the upper dead point of 0.degree. to the crank angle 60.degree. in the rotation of the crank, the work is unclamped from the feed bars for the next angular distance of 60.degree. in the crank rotation, the work is then processed, the feed bars are moved in the return stroke for the next angular distance of 120.degree. in the crank rotation, the feed bars are stopped again and the work is clamped by the feed bars for the next angular distance of 60.degree. in the crank rotation. As the device for driving the feed bars in the advance and return strokes in the transfer press, the following devices have been proposed and practically employed, that is, (a) a pneumatic or oil cylinder-type drive device, (b) a cam and lever-type drive device, (c) a chain-driven drive device, (d) a rack and pinion-type drive device and (e) a planetary gear mechanism. However, the convention feed bar drive devices referred to hereinabove have their respectively inherent advantages and disadvantages with respect to performance, cost and versatility and in consequence, the conventional feed bar drive devices were not perfectly satisfactory.